Mal-PEG-SCM (MW 2000) is a linear heterobifunctional PEG compound that features maleimide and NHS ester (succinimidyl) groups. It serves as a significant PEGylated crosslinker. The maleimide moiety reacts with thiols, SH groups, mercaptans, or sulfhydryls, while SCM stands for succinimidyl carboxymethyl ester, which can interact with primary amines. Maleimide contains a reactive C=C double bond, sensitive to light or oxygen.